Abstract
The effect of maternal crowding on the offspring sex ratio of a cereal aphid parasitoid Lysiphlebus delhiensis (Subba Rao & Sharma) (Hymenoptera: Braconidae) was examined. Increasing the number of mothers per host-patch always increased the proportion of males in the population (p). The extent of variations in p at different levels of maternal crowding was compared with the prediction of the Hamiltonian LMC model, i.e. p = (n-1)/2n, where n = number of mothers/host-patch. The perception of trace odours of conspecific females induced haploid oviposition. Differential mortality of the larvae by sex in superparasitised hosts, shifting the p towards sons has been discussed. The inversely parasitoid-density-dependent p indicates that for obtaining maximum number of female progeny, the ratio of female parasitoid to the host in mass breeding should not be less than 1:100 at a time.
Résumé
L’effet de la surpopulation maternelle sur le rapport des sexes dans la progéniture d’un parasitoüde du puceron des céréales Lysiphlebus delhiensis (Subba Rao & Sharma) a été examiné. L’augmentation du nombre de mères par hôte s’accompagnait toujours d’une augmentation de la proportion des mâles dans la population (p). Le degré des variations de p à différents niveaux de surpopulation maternelle a été comparé à la prédiction du modèle Hamiltonian LMC, à savoir p = (n-1)/2n, où n = le nombre de mères/hôte. La perception des traces d’odours de femelles conspécifiques induisait la production d’oeufs haploüdes. La mortalité larvaire differentielle par sexe chez les hôtes superparasites, faisant basculer les valeurs de p en faveur des mâles a été discutée. Les valeurs de p en rapport inverse de la densité du parasitoüde montre que pour obtenir un nombre maximal de femelles dans la progéniture, le rapport du parasitoüde femelle par hôte en élevage en masse ne devrait jamais être inférieur à 1:100.
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Biswas, S., Singh, R. Offspring Sex Ratio of a Cereal Aphid Parasitoid, Lysiphlebus delhiensis (Subba Rao & Sharma) in Response to Maternal Crowding. Int J Trop Insect Sci 16, 287–291 (1995). https://doi.org/10.1017/S1742758400017306
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DOI: https://doi.org/10.1017/S1742758400017306
Key Words
- Lysiphlebus delhiensis
- Melanaphis sacchari
- Zea mays
- aphids
- parasitism
- Aphididae
- biological control
- sex ratio
- parasitoid density
- maternal crowding